Skip to Main Content

++
Figure 43-1. Normal Capnogram
Graphic Jump Location

(I) Anatomic dead space.

(II) Transition from anatomic dead space to alveolar plateau.

(III) Alveolar plateau (typically slight upward slope).

Reproduced from Longnecker DE, Brown DL, Newman MF, Zapol WM. Anesthesiology. Figure 31-7. Available at: http://www.accessanesthesiology.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.

++

  • Healthy lungs: 2–3 mm Hg awake, 5–8 mm Hg anesthetized
  • COPD: up to 10 mm Hg awake, 15–20 mm Hg anesthetized
  • Further increased by heat/moisture exchanger
  • Further increased by V/Q mismatch: PE, hypovolemia, lateral position

++
Table Graphic Jump Location
Favorite Table | Download (.pdf) | Print
Causes of Acute Changes in Capnogram
Exponential decreaseIncreased dead space (suspect PE or arrest)
Sudden drop to zeroLikely circuit disconnect
Gradual decrease but not to zeroLeakage or partial obstruction of airway
Air embolism, PE
Drop in CO: hypovolemia, IVC cross-clamping
Decrease in metabolic rate: hypothermia, deep anesthesia
Gradual increaseProlapse of expiratory valve or decreased minute ventilation
Sudden increaseRelease of tourniquet, aortic unclamping, MH
++
Figure 43-2. Changes in Capnogram in Different Disease States
Graphic Jump Location

(A) A normal capnograph demonstrating the three phases of expiration: phase I—dead space; phase II—mixture of dead space and alveolar gas; phase III—alveolar gas plateau. (B) Capnograph of a patient with severe chronic obstructive pulmonary disease. No plateau is reached before the next inspiration. The gradient between end-tidal CO2 and arterial CO2 is increased. (C) Depression during phase III indicates spontaneous respiratory effort. (D) Failure of the inspired CO2 to return to zero may represent an incompetent expiratory valve or exhausted CO2 absorbent. (E) The persistence of exhaled gas during part of the inspiratory cycle signals the presence of an incompetent inspiratory valve. Reproduced from Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesiology. 4th ed. Figure 6-25. Available at: http://www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.

1. Swedlow DB. Capnometry and capnography: the anesthesia disaster early warning system. Semin Anesth. 1986;3:194–205.
2. West JB. Respiratory Physiology: The Essentials. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2000.
3. Berengo A, Cutillo A. Single-breath analysis of carbon dioxide concentration records. J Appl Physiol. 1961;16:522–530.

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.

Ok

About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessAnesthesiology Full Site: One-Year Subscription

Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessAnesthesiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.